Building A Replica Aircraft

Part Three

Construction Details

Wings and Covering

• The human brain is a wonderful organ. It starts to work as soon as you are born and doesn't stop until you get up to deliver a speech."

• -- George Jessel, American actor

Brief Review

• After obtaining a partially complete Graham Lee 7/8 scale Nieuport 11 project – I decided to reconfigure it to resemble a 1929 Boeing F4B-2 US Navy Fighter.

• Boeing developed the F4B in mid 1928 at company expense as a small light weight fighter for the US Navy.

• The -1 and -2’s had a unique structure as the fuselage was bolted/gusseted aluminum tubing. Wings were all wood (in fact the last of the wooden wing fighters in the Navy).

F4B-2

Objectives

• Utilize as much of the original project as possible.

• All modification must not compromise structural integrity.

• Keep as light as possible – don’t go “overboard” on detailing!

• Maintain the look of the Boeing with out becoming “anal”.

• Have some fun!!

Lower Wing

• The lower wings would require an increase in the bottom chord to fit the profile of the F4B.

• Drawings were developed of the lower wings with F4B outlines within the original span dimensions but with an increase in chord.

Lower Wings

• Began construction by first deconstructing existing lower wings and salvaging Spars and some ribs.

Lower Wings

• To more accurately portray the F4B new ribs of a longer chord where required.

Lower Wings

• The wing tips were fabricated next.

Lower Wings

• Construction

Lower Wing

• Construction Modified Strut mounts to accommodate “N” strut.

– Attempt to remove camber from lower wing

Lower Wing

• Construction

– Modified rib construction from the spar aft

Upper Wing

• Removed sweep out of wings and modified wing tip shape

• Another departure from the Graham Lee design. I decided to construction the wing in three sections rather than the two in the plans.

1. Simplify field assembly should I decide to transport aircraft by trailer.

2. Incorporate Access/Inspection panel to make aileron controls more accessible.

3. Incorporate “plug-in” wing attachments by using 3 nested tubes in main and 2 in the aft spar.

4. Allowed a more manageable way to establish the proper angle of incidence of the main wing.

Center Section Construction

Top Wing Panels

• The top wing panels were also deconstructed.

• Most of the original wing ribs, compression struts and fittings were reused, however, new spars were procured and installed.

• As with the lower wings, new wing tips were constructed to reflect the wing profile of the F4B.

Top Wing Panels

Utilized the Center Section to “Jig” the inboard spars while locating and installing Compression Struts and Drag/Anti Drag cables

Using Tip Bow to determine length of rear spar.

Top Wing Panels

• Cut and fit spars to wing tip and temporally fasten with Clecos. • Repeat for Left Side Panel

Top Wing Panels

Hung wings to locate “N” strut fittings without having to work around wing ribs and wing interior structure. Could only work one side at a time due to shop size but hung left top panel on airframe to even load on the center section.

Struts

Next step was to level the top wing then set the dihedral in the bottom wing. With that done I use masking tape to visualize the struts and the needed placement of the various fittings. The resulting dimensions were transferred on to strips of plywood to further determine lengths and angles needed in fabricating the struts.

Struts

Top Wing Panel

Top Wing Panel

Top Wing Panels

Top Wing Panels

Pre-Cover

Assembled all components to check fit, angle of incidence and dihedral. Final drilling of struts and fabrication of all flying/landing wires followed.

April 2013

Pre-Cover

237 pounds

Removed wheels to establish a more stable airframe and also allowed the “short guy” to better reach the upper wing! (Should have thought of that earlier!)

Pre - Cover

May 2013

Covering

• Dilemma which covering process to use : – Poly Fiber – the standard for many years – Stewart’s – touted as “eco” friendly – Oratex – new process to the US – no painting.

• Pro’s – All use a polyester fabric – Poly Fiber has the largest user base and instructions are

excellent and has a large selection of colors. – Stewart’s utilizes water base glues and finishing materials

and most if not all of the same selection of colors as Poly Fiber.

– Oratex utilizes a water base adhesive and the finish is pre-coated. Finished weight is as much as half as much as Poly Fiber

Covering

• Cons – Poly Fiber uses volatile materials that smell and can be

hazardous to health.

– Stewart’s doesn’t smell as bad but still induces fumes when sprayed that prolonged exposure should be avoided.

– Poly Fiber and Stewart’s would require investment in equipment and facilities I did not own (namely good quality spray equipment and a finishing booth).

– Oratex has limited color availability and doesn’t produce a “wet” look finish. Limited instruction manual. Materials are more expensive than equivalent from Poly Fiber or Stewarts.

Covering

• Decision

– Oratex

• No exposure to hazardous chemicals.

• Available colors matched my needs.

• A “wet” finish would not be appropriate for a 1930 vintage replica.

• No need for painting equipment, paint booth, extra lighting, dust free environment, etc. (i.e. avoided expense).

• Significant savings in installed weight and work effort.

Empennage (Tail Group)

Empennage (Tail Group)

Lower Wings

Lower Wings

Lower Wings

Upper Wings

Fuselage

Fuselage

Wheels

Covering Details

• Empennage 56.5 hours 2.6 lbs

• Wings 224.5 12.7

• Fuselage 40.0 2.0

• Wheels 12.0 0.4

Total 333.0 hours 17.7 lbs

• Poly Fiber (med. weight) Estimate 42.6 lbs

• My original Oratex 6000 estimate (w/o wheels) 17.3 lbs

• Weight savings @ 25Lbs or 5% of 475 projected empty weight.

Snack & Chat April 2014

Initial Weight and Balance

455 lbs as shown

Projected empty 475-485 Gross 750 lbs

May 1, 2014

To be Continued !

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